The defect detector is a device that lets Vee know if there's anything wrong with chuggers as they pass by its scanners. Unfortunately, it seems to be malfunctioning! Eddie takes it off to the repair shed and Emery, wanting to be helpful, takes its place. But, worried that he might miss something, Emery sends nearly everyone to the repair shed, creating chaos in the depot! Emery feels bad that he's caused so much work for Vee and wishes he could make up for it. He has an idea. If the detector could talk, it wouldn't have to do everything through Vee. Dr Ling and Eddie think it's a great idea and they update the detector so that it speaks. And they know the perfect voice to use Emery's!